1. Technical Background
The present invention relates generally to medical devices, and more particularly to a vascular filter and delivery system.
2. Discussion
Vascular filters may be used for a variety of therapeutic applications, including implantable vena cava filters for capturing thrombus, or for distal protection during a vascular procedure.
The present invention relates to a filter system including a vascular filter that can be placed inside a body passage or cavity, such as a blood vessel, through a catheter consisting of a tubular basic body with a distal end, a proximal end and a lumen extending in between the ends. The vascular filter can be received in a compressed state inside the lumen, and the catheter is provided with an ejection device which can be used to eject the vascular filter from the distal end of the catheter. The filter may be implanted either permanently or temporarily.
Vascular filters are often made of an elastic or so-called "memory" material. Prior to actually positioning the vascular filter according to the known technique inside the blood vessel, the filter is arranged in a compressed state in the catheter. By means of an ejection member, the filter may be pushed from the open distal tip of the catheter into the blood vessel.
Many prior vascular filters expand from the compressed state inside the catheter lumen to an enlarged or deployed state, when released or deployed at the desired site for treatment. Some vascular filters tend to resiliently expand to that deployed state, which facilitates ejection from the catheter. Also, this resilient outward pressing may resist longitudinal movement from the desired site or compressive external forces.
It is also possible, however, that the resilient expansion by a filter may cause it to push off in a resilient manner against the distal end of the catheter. This possible longitudinal pushing or jumping tendency may cause a vascular filter to rest in some location other than the desired site. Consequently, accurate positioning of the filter inside the blood vessel may require some measure of skill.
Accordingly, it is desirable to provide a vascular filter capable of being more easily positioned accurately, and which tends to proceed smoothly and predictably during deployment.
One embodiment of the present invention is therefore to provide a vascular filter for use with a catheter to introduce the filter, wherein a brake is provided. The brake acts between the filter and catheter which may tend to control ejection by means of engaging the lumen. This engagement may of course be frictional, and the brake may be provided on the filter or the catheter, or may consist of cooperating components on both filter and catheter.
With a vascular filter and catheter system according to the present invention, an accelerating force exerted by the vascular filter on the distal tip of the catheter can be resisted or even negated by the brake. The brake preferably frictionally opposes the movement of the filter out of the catheter. Consequently any expansive accelerating force exerted during ejection of the filter is controlled, at least any particular expanisive force which may cause an unexpected longitudinal advance in relation to the distal tip of the catheter.
The brake may have any of a number of embodiments, as will be discussed in the detailed explanation below which are given by way of example. For example, the brake may have been biased, or the brakes may form a unit with the filter, or may act in unison with additional brakes.
These and various other objects, advantages and features of the invention will become apparent from the following description and claims, when considered in conjunction with the appended drawings.